What The Heck Is It And How Does It Keep Me Warm?

There are many pros to using down for insulation. It has the best warmth-to-weight ratio, it is generally longer lasting, it’s extremely compressible and very warm. But did you know that it’s not all the same?

Enter Fill Power.

Fill power, is a measure of the quality and loft of the down used in a product, like down jackets and sleeping bags. It represents the ability of down clusters to trap air and create insulating pockets. The higher the fill power, the better the down's ability to provide warmth and breathability while remaining lightweight.

So What Do The Numbers Mean?

Fill power is typically expressed as a number, such as 650, 700, 800, or more. This number indicates the volume in cubic inches that one ounce of down will occupy when it's allowed to fully loft.

For example, 800-fill power down will take up 800 cubic inches per ounce. Higher fill power down is fluffier, meaning it can trap more air and provide better insulation. Because it’s fluffier it makes it warmer for its weight, more compressible and much more efficient.

So, when you see a product with a high fill power rating, you can expect it to be warmer (by weight) and more compressible, making it a great choice for cold weather activities where weight, pack size and warmth are critical.

A key thing to note:
Fill weight is often something that goes under the radar. Fill weight will reflect the warmth a garment will provide.

For example:
30g of 800 Fill down won’t nearly be as warm as 150g of 500 Fill down. The warmer jacket in this example will be much bulkier and less packable by comparison.

When choosing a jacket, it's important to remember the goals you are trying to achieve. If it is to simply stay warm this winter, a 600 Fill parka is probably going to be the right choice. However, if you are looking for a layering piece that is lightweight, extremely packable and versatile - an 800 Fill jacket will probably be something worth considering.

So the next time you are shopping for a warm jacket or sleeping bag, remember that not all down is used in the same way. Consider your outdoor goals and how this piece of clothing will help.